Various types of motion systems are routinely employed in the technical fields of robotics, automation, machining, medical imaging, computer disk drives, and a number of other fields of technology. A motion control system employed in such motion systems typically includes a digital or analog controller responsive to command inputs, an amplifier/driver, and a linear or rotary actuator coupled to a mechanical system, such as a mechanical tool or a joint of a robotic arm. Motion control systems may be implemented for operation in either an open-loop or closed-loop configuration. In a closed-loop configuration, feedback sensors are generally employed to provide the controller with data concerning the actuator and mechanical system during operation. A high degree of control is required in many types of precision motion systems, as any unintended residual vibration or movement during operation of the system may have costly and unintended consequences. Undesirable vibration within a motion system employed in a medical imaging system, for example, may result in various types of imperfections in an imaging process. Unacceptable levels of surface roughness, by way of further example, may result from unwanted vibration occurring within a motion system employed in high precision machining equipment. It is well appreciated in the art that unwanted vibrations or oscillations are of primary concern in many high-precision motion system applications. A number of techniques have been developed to reduce undesirable vibrations or oscillations associated with movement of a motor in a motion system.
U.S. Pat. No. 5,111,590 describes a computer aided kinematic transducer link system for assessing contouring accuracy of machine tools. U.S. Pat. No. 5,767,380 describes a measuring arrangement for checking geometrical and dynamic accuracy of two numerically controlled and displaceable machine elements. U.S. Pat. No. 5,900,938 describes a laser measurement system for rapid calibration of machine tools including a measurement enhancement apparatus which enables an existing standard single degree of freedom laser interferometry system to simultaneously measure up to four added degrees of freedom.
Calibration equipment with plurality of axes of rotation suitable for rotatable connection to a fixed reference point of a tool or robot have been described in U.S. Pat. No. 5,909,939 and U.S. Pat. No. 6,205,839. Ball bar gauges for obtaining accuracy in numerical control machines are described in U.S. Pat. No. 4,435,905, U.S. Pat. No. 4,884,348, U.S. Pat. No. 5,052,115, U.S. Pat. No. 5,214,857, U.S. Pat. No. 5,428,446, U.S. Pat. No. 5,428,446, U.S. Pat. No. 5,533,271, U.S. Pat. No. 5,647,136, U.S. Pat. No. 5,681,981 U.S. Pat. No. 5,720,209 and U.S. Pat. No. 5,813,128. Jointed movable coordinate positioning apparatuses are described in U.S. Pat. No. 4,777,818, U.S. Pat. No. 5,791,843 and U.S. Pat. No. 6,086,283.
Although many of these previous approaches would appear to provide a measure of unwanted motion errors including vibration, such techniques often fail to provide the requisite level of precision measuring or simultaneous execution of measurement desirable for many applications. Further many of the apparatuses are time intensive to set up and execute and costly to operate. The present invention provides a measuring apparatus for precision machinery which measures the relative positioning accuracy between tool tip and workpiece defined by six different motions simultaneously.